Finally, a use for ground up fish bones! Turns out they neutralize harmful lead in soil:

It's not so much the bones themselves that make the difference as the calcium phosphate they contain. When fish bone meal is mixed into the soil, the calcium phosphate combines with the lead to form pyromorphite, a harmless, consumable crystalline mineral. But the great part about this solution, put forward by the Environmental Protection Agency , is not its novelty- it's been around for at least 15 years. Compared to the expensive and wasteful practice of removing lead-contaminated soil, the fish bones method is remarkably affordable. The NYT writes: Although the [EPA] does not record its spending by individual contaminants, it is safe to say it has spent millions of dollars on lead cleanup. If the new techniques of neutralizing toxic metals catch on the money would go further by replacing the method of digging up and disposing of hundreds of thousands of tons of soil tha...